Spark plug



Sept. 10, 1935.

c. LEHMAN ET AL SPARK PLUG Filed July 12, 1954 Patented Sept. 10, 1935UNITED STATES y 2,014,260 SPARK PLUG Charles Lehman and Otto E. Lehman,Philadelphia, Pa.

Application July 12, 1934, Serial No. 734,766

'7 Claims.

Ourinvention relates to new and useful improvements in a spark plug andhas for one of its objects to provide an exceedingly simple andeilective device of this character which is relatively inexpensive inthe cost of manufacture although strong and durable.

Another object of this invention is to provide an air-cooled spark plughaving a spacious air chamber extending substantially from one end tothe other.

Another object of the present invention is to so construct the sparkplug that it will be oil, heat and carbon resisting.

Another object of the invention is to provide a spark plug including abody closed at its lower or inner end except for an opening throughwhich the porcelain protrudes, said opening being closed by theporcelain and a gasket on which a shoulder of the porcelain is seated,thereby preventing the influx of oil to the body or shell, which oiloften accumulates and produces incrustations of carbon.

A further object of our invention is to provide, in combination, a sparkplug having a central electrode, and a unique means for attachment of acable terminal thereto.

A still further object of the invention is to construct a spark plugincluding a central electrode connected with a head, the latter beingfashioned so as toprevent rotation thereof in the porcelain core andhaving a spring pressed clamping Washer provided with a concavo-con Vexrib for coaction a specially shaped cable terminal. Withk these andother endsin viewthis invention consists of the details of constructionand combination of elements hereinafter set forth and then specificallydesignated by the claims.

In order that those skilled in the art to which this inventionappertains may understand how to make and use the same, we will describeits construction in detail, referring by numerals toy the accompanyingdrawing forming a part of this application, in which:-

Fig. 1 is a side elevation of a spark plug constructed in accordancewith our invention.

Fig. 2 is a longitudinal or vertical section thereof, with the centralelectrode and its component parts shown in elevation.

50 Fig. 3 is a view of the upper end of the central electrode and theattachable head structure there- Fig. 4 is an upper end View of Fig. 1.

Fig. 5 is a section at and on the line 5-5 of 55 Fig. 2.

Fig. 6 is a section at and on the line 6-6 of Fig. 2, and

Fig. '7 is a section at and on the line 'I--'I of Fig. 2.

In carrying out our inventioin as herein em- 5 bodied, I0 represents thebody or shell of the spark plug provided with a shank II, which hasexternal threads I2, for mounting the spark plug in the cylinder of anengine.

Within said body or shell is formed a spacious 10 air chamber I3,preferably larger at its upper end than at its lower o-r inner end andin the lower or inner end of the body or shell is produced alongitudinal hole I4, for a purpose to be presently described, and saidhole communicates with the 15 air chamber.

In the side walls of the body or shell are a number of transverse orradial apertures I5 which communicate with the upper part of the aircharnber and function as air inlets and outlets. 20

A porcelain core I6 is inserted into the air chamber through the upperend of the body or shell and said core has a reduced lower end I1 whichprojects through the hole I4. Said reduced end of the porcelain core isof a size that snugly 25 ts the hole I4, but has sufficient tolerance topermit expansion of the parts, whereby the hole is partly closed toprevent the entrance of oil into the oil chamber. The closure is madecomplete by a gasket I8, resting on a seat I9 with- 30 in the body o-rshell, and the shoulder 2D formed by the differences in diameter of thereduced end and the contiguous part of the core.

An intermediate part of the core, which is located within the body orshell, is also reduced in 3D diameter for substantially the length ofthe air chamber so that only a limited amount o-f the space of the airchamber will be occupied, leaving a large space for the circulation ofair. The porcelain core is held in place by a gland nut 2| 40 whichengages a shoulder 22 on the core and has threaded engagement with thebody or shell.

In the longitudinal center of the porcelain core is the centralelectrode 23 and the lower end of said electrode protrudes beyond thelower end of the core in proximity to the return or ground electrode 24.The end of the porcelain core from which the lower end of the centralelectrode protrudes is convex so that any liquid reaching the same willreadily ow or drip therefrom.

On the upper end of said central electrode 23 is mounted a head 25,consisting of a post 26 which originally is preferably round in crosssection throughout its entire length and with a reduced upper or outerend portion 21 to provide a shoulder 2B. On the post 26, intermediateits ends, is a collar 29, approximately the same diameter as the upperor outer end of the porcelain core, against which it rests. The lowerend of the post has a hole in it to receive the uppei` end of thecentral electrode and after the parts are assembled, said lower end ofthe post is swaged into an angular` relatively thin and wide skirt 3D,thereby fixing the head to its electrode. This skirt is embedded in theporcelain core and prevents the head from turning relative to said core.

A clamping washer 3| is slidably and rotatably mounted on the post 26and has a concavo-convex rib formed therein to provide a diametricalgroove 32 in the under or inner face of said clamping washer, withportions of said groove on opposite sides of the post. This clampingwasher is forced toward the collar 29 by a spring 33 positioned betweenthe washer and a cap 34, mounted on the outer end of the post.Preferably, the cap is placed on the reduced outer end of the post incontact with the shoulder 28 and said post then set up as a rivet head,as at 35.

A connecting terminal 36, Figs. l and 4, is provided for use with theattaching structure and is to be fastened to a cable or other electricalconductor. This terminal has the usual legs to straddle the post andeach leg is provided with a transverse ridge or projection 31 forregistration with the groove 32. The ridge 31 and the groove 32 are soshaped that when sulicient force is applied, the terminal 36 can bereadily attached or d-etached, but accidental separation is prevented.Since the clamping washer is loose on the post, and since the terminalonly rests on the collar, said terminal may be turned around the postinto any desired position without detaching the same.

From the foregoing it will be obvious that when the spark plug is in useno oil can enter the lower part of the body or shell, therebyeliminating one of the causes of electrical leakage and the formation ofcarbon deposits. As heat also enters into the cause of the formation ofcarbon, the chance of such formation is further reduced to a minimum byproviding means to cool the parts of the spark plug as above described.

By using the construction herein described, especially in connectionwith automobile and airplane engines, air will be forced toward thespark plug or plugs by the cooling fan or propeller. The air will entersome of the apertures I and circu late about the spacious air chamber I3and then exit through others of said apertures I 5. Because of thespaciousness of the air chamber, large quantities of air can circulateand will maintain the parts of the spark plug which are subjected tohigh degrees of heat, at a relatively low and even temperature'.

Of course we do not wish to be limited to the exact details ofconstruction herein shown and described as these may be varied withinthe scope of the appended claims without departing from the spirit ofour invention.

Having thus fully described our invention, what we claim as new anduseful, is:-

l. A spark plug comprising a body or shell having a threaded portion andprovided with a spacious air chamber extending from adjacent the upperto adjacent and past the lower threaded portions of the body with alongitudinal. hole in the bottom and radial apertures in the side wallscommunicating with the air chamber, a core of insulating materialmounted in the body or shell and having a reduced end tted in the bottomhole to close the same, said core having a large portion thereof withinthe body or shell reduced in size, a central electrode mounted in saidcore, and another electrode carried by the body or shell and locatedadjacent the inner end of the central electrode.

2. The structure in claim l, in combination with a gasket locatedbetween a shoulder on the core and a seat at the bottom of the airchamber to further close the hole at the bottom of the body or shell.

3. In a device of the kind described, a body or shell including apartially threaded shank and having a spacious air chamber extendingfrom adjacent the upper portion of the body proper to adjacent and pastthe threaded portion of the shank and having radial apertures in theside walls communicating with said air chamber, and a porcelain corecarrying an electrode and mounted in the body or shell, said core havingthat portion within the air chamber considerably reduced incircumference.

4. A spark plug comprising an air cooled body or shell, a porcelain corein .said body or shell with both ends extending beyond the respectiveends of said body or shell, said core substantially closing the lowerend of the body or shell, means at the upper end of said body or shellto hold the core in place, a central electrode in the core,

a head structure including a post, a substantially triangular thin skirtswaged from the lower portion of said post and embedded in the core, theswaging of said post fixing the head structure to the electrode, acollar on said post engaging the upper end of the core, a clampingwasher slidably and rotatably mounted on the post and having a groove inits under face to receive a ridge on a cable connecting terminal, a capmounted on the upper end of the post, and a spring on the post betweenthe cap and clamping washer to force the latter toward the collar.

5. The structure in claim 4, wherein the cap is' mounted on a reducedend of the post and contacts a shoulder produced by the differences indiameters between said reduced end and the contiguous portion of thepost and wherein said cap is held in place by a rivet head formed on theend of the post.

6. In a spark plug, a porcelain core, a central electrode in said core,a head structure including a post having a reduced upper end, a shoulderat the junction between said reduced upper end and the contiguous partof the post, the lower end of said post having a hole for registrationwith the upper end of the electrode, a skirt swaged from the lower endof the post to fix the head structure to the electrode and embedded inthe core to prevent rotation of said head structure relative to saidcore, a collar on said post, a clamping washer slidably and rotatablymounted on the post and forming a clamp with the collar, said clampingwasher having a groove in its under face for registration with a ridgeon a cable terminal, a cap mounted on the reduced end of the post, arivet head formed from the extreme outer end of the post to hold saidcap in place, a spring between said cap and the clamping washer to forcethe latter toward the collar, a hollow body or shell having a shank forprojection into an engine and provided with apertures above the shankcommunicating with' the interior of the body or shell and functioning asinlets and outlets for air, a gasket in the bottom of the body or shell,said core and associated parts being mounted in the body or shell withthe lower end of said core protruding through a hole in the bottom ofthe body or shell, a shoulder on said core to engage the gasket andclose the hole, that portion of the core within the body Lor shell beingspaced from the side walls of the body or shell to form an air chamber,means to hold said core in the body or shell, and another electrode onthe body or shell for co-action with the central electrode.

7. In a spark plug, a body or shell having an air chamber extendingapproximately all the way from one end to the other with a longitudinalhole of smaller diameter than the air chamber in the bottom and radialapertures in the side walls communicating with the upper portion of saidair chamber, a single seat at the bottom of the air chamber, a porcelaincore mounted in the body or shell and having a reduced lower endprojecting through the hole in the bottom of the body or shell, theextremity of said reduced end being convex, a shoulder on the core atthe top of the reduced end for coaction with the seat, a gasket betweenthe seat and shoulder, a central electrode embedded in the porcelaincore and exposed only where it protrudes from the convex lower extremityof said core, and another electrode carried by the body or shell andspaced from the central electrode.

CHARLES LEHMAN.

OTTO E. LEHMAN.

